PHP Version 4.2.2

[eluser]jleequeen[/eluser]
Unfortunately I work in an environment that is ages behind in php upgrades (I have no control over this). We are stuck at 4.2.2 and it looks like the earliest that we could move to PHP5 will be six months from now. I'm anxious to use CI on a small project that will be perfect in size for my first application. I'm wondering since CI requirements are 4.3.2 what exactly would break if you tried to run it on 4.2.2?